Upload & Sell: On
I think both Canon and Nikon use skim-the-cream pricing for new product introductions with the expectation that prices will settle lower once first-adopter demand has been satisfied.
That's Econ 101. You introduce at a price you believe it will sell for, knowing demand amongst some sectors (early adopters) will be greater than others. As initial demand wanes, you gradually lower price to keep supply/demand balanced.
The early adopters are more apt to sing the lens's praises, so in the mean time you get free forum marketing, have people waiting for a "sale" or price drop, then once the price hits that barrier...more sales.
Now as to the 24-70/4 specifically -- I still can't figure that one out